The Canyon County Highway District completed installation of 15 new traffic signals at intersections across the county’s fastest-growing corridors in February, a $4.8 million project that represents the largest single-year signal deployment in the district’s history. The new signals target intersections where residential development has pushed traffic volumes beyond the capacity of existing stop-sign controls, creating dangerous cross-traffic movements, long wait times, and a rising pattern of angle crashes that prompted the signal installations.
The 15 new signals are concentrated in three primary areas: the Star-Middleton corridor along Highway 44 (5 signals), southern Nampa along Lake Lowell Avenue and Happy Valley Road (6 signals), and the Caldwell-Nampa corridor along Ustick Road and Karcher Road (4 signals). These areas have experienced the most intense residential development activity in Canyon County over the past three years, with thousands of new homes generating tens of thousands of additional daily vehicle trips on roads that were designed for rural traffic levels.
Why New Signals Were Needed
Highway district traffic engineer Mike Woodruff said the signal installations were triggered by traffic volume and safety criteria established in the district’s traffic management plan. Each of the 15 intersections had met or exceeded the federal Manual on Uniform Traffic Control Devices warrant thresholds for signalization — meaning that traffic volumes, crash history, and pedestrian activity levels at each location justified the installation of a traffic signal based on nationally recognized engineering standards.
“These aren’t arbitrary installations — every one of these signals was warranted by the data,” Woodruff said. “When an intersection that was handling 5,000 vehicles a day five years ago is now handling 15,000, a stop sign is no longer adequate. The signal provides the controlled, predictable traffic flow that prevents crashes and keeps traffic moving.”
The 15 intersections collectively experienced 47 reported crashes in 2025 prior to signal installation, including 12 injury crashes and one fatality at the Middleton Road-Ustick Road intersection. Angle crashes — where a vehicle pulling from a stop sign is struck by through traffic — accounted for 68% of all crashes at the 15 locations, a pattern that traffic engineers identify as the primary indicator of the need for signal control.
Adaptive Signal Technology
All 15 new signals feature adaptive control technology that adjusts signal timing in real time based on traffic demand detected by embedded sensors and overhead cameras. During peak commute hours, the signals prioritize the heavier traffic movements; during off-peak periods, they revert to shorter cycles that minimize wait times for all directions. The adaptive technology is connected to the highway district’s traffic management center in Caldwell, allowing engineers to monitor and adjust signal operations remotely.
Funding and Taxpayer Cost
The $4.8 million project — averaging $320,000 per signal installation — was funded through a combination of development impact fees ($3.2 million) and federal Highway Safety Improvement Program grants ($1.6 million). No property tax funds were used. Impact fees are collected from developers at the time of building permit issuance and are legally restricted to transportation infrastructure improvements necessitated by new development.
What Comes Next
The highway district has identified 8 additional intersections that are approaching signal warrants and will likely require installation within the next two years as development continues. Residents with traffic safety concerns about specific intersections can submit requests to the Canyon County Highway District at cchd.idaho.gov or call 208-454-7300. For statewide transportation news, visit Idaho News.